First effective date from a table sql - sql

Question

There is a table asg_table with columns effective_start_date and effective_end_date.
asg_table:
asg_number effective_start_date effective_end_date location department action_code
1 01-jan-2019 20-jan-2019 HR HIRE
1 21-JAN-2019 18-FEB-2019 Vietnam HR CHANGE_ASG
1 19-FEB-2019 31-DEC-4712 Vietnam Manegment CHANGE_ASG
2 02-mar-2019 29-Apr-2019 Peru hr HIRE
2 30-Apr-2019 31-dec-4712 Vietnam HR CHANGE_ASG
I want to create a query to find the first effective_start_date of the employee when the action_code is HIRE, and the location is null.
Is there a function to do so ?

Answer 1

It depends on what order you want to perform the filtering:
Oracle Setup:
CREATE TABLE asg_table ( asg_number, effective_start_date, effective_end_date, location, department, action_code ) AS
SELECT 1, DATE '2019-01-01', DATE '2019-01-20', NULL, 'HR', 'HIRE' FROM DUAL UNION ALL
SELECT 1, DATE '2019-01-21', DATE '2019-02-18', 'Vietnam', 'HR', 'CHANGE_ASG' FROM DUAL UNION ALL
SELECT 1, DATE '2019-02-19', DATE '4712-12-31', 'Vietnam', 'Management', 'CHANGE_ASG' FROM DUAL UNION ALL
SELECT 2, DATE '2019-03-02', DATE '2019-04-29', 'Peru', 'HR', 'HIRE' FROM DUAL UNION ALL
SELECT 2, DATE '2019-04-30', DATE '2019-05-01', 'Vietnam', 'HR', 'CHANGE_ASG' FROM DUAL UNION ALL
SELECT 2, DATE '2019-05-01', DATE '2019-06-01', 'Vietnam', 'HR', 'FIRE' FROM DUAL UNION ALL
SELECT 2, DATE '2019-06-01', DATE '4712-12-31', NULL, 'HR', 'HIRE' FROM DUAL;
Query 1:
If you want to filter where location is NULL and action_code is HIRE first and then find the earliest effective_start_date for each asg_number then:
SELECT *
FROM (
SELECT t.*,
ROW_NUMBER() OVER ( PARTITION BY asg_number ORDER BY effective_start_date ASC ) rn
FROM asg_table t
WHERE location IS NULL
AND action_code = 'HIRE'
)
WHERE rn = 1
Output:
ASG_NUMBER | EFFECTIVE_START_DATE | EFFECTIVE_END_DATE | LOCATION | DEPARTMENT | ACTION_CODE | RN
---------: | :------------------- | :----------------- | :------- | :--------- | :---------- | -:
1 | 2019-01-01 | 2019-01-20 | null | HR | HIRE | 1
2 | 2019-06-01 | 4712-12-31 | null | HR | HIRE | 1
Query 2:
If you want to find the earliest effective_start_date for each asg_number and then filter where location is NULL and action_code is HIRE first then:
SELECT *
FROM (
SELECT t.*,
ROW_NUMBER() OVER ( PARTITION BY asg_number ORDER BY effective_start_date ASC ) rn
FROM asg_table t
)
WHERE location IS NULL
AND action_code = 'HIRE'
AND rn = 1
Output:
ASG_NUMBER | EFFECTIVE_START_DATE | EFFECTIVE_END_DATE | LOCATION | DEPARTMENT | ACTION_CODE | RN
---------: | :------------------- | :----------------- | :------- | :--------- | :---------- | -:
1 | 2019-01-01 | 2019-01-20 | null | HR | HIRE | 1
db<>fiddle here

Answer 2

I hope there is some column to identify the employee.
Try this:
Select * from
(Select t.*,
Row_number() over
(partition by t.employee_id order by t.effective_start_date) as rn
From asg_table t
Where t.location is null
AND t.action_code = 'HIRE')
Where rn = 1;
Cheers!!

Answer 3

SELECT MIN(effective_start_date) OVER(PARTITION BY action_code ORDER BY action_code) AS first_effective_start_date,A.*
FROM asg_table A
WHERE LOCATION IS NULL
AND action_code ='HIRE'
;
If you would like to get all records along with first_effective_start_date as a separate column.
Cheers!!

Answer 4

No need for function
SELECT * FROM TABLENAME WHERE EFFECTIVE_START_DATE IN (CASE WHEN ACTION_CODE='HIRE' AND LOCATION IS NULL THEN EFFECTIVE_START_DATE END)
On top of the above query use
ROW_NUMBER ANALYTICAL FUNCTION
to get the first
EFFECTIVE_START_DATE

Answer 5

SELECT
(SELECT MIN(effective_start_date) FROM asg_table) as first
FROM
asg_table
WHERE
location IS NULL AND action_code = "HIRE"
LIMIT 1;
Enjoy!